Exploring the Anticorrosive Effects of an Imidazole Derivative on Mild Steel in Sulfamic Acid: A Combined Experimental and Theoretical Perspective

In the present study a substituted imidazole derivative (2E)-2-[(2-butyl-4-chloro-1H-imidazol-5-yl)methylidene]hydrazine-1-carbothioamide (IMTSC) has been synthesised and characterized using FTIR, ¹H NMR and ¹³C NMR spectroscopic techniques. The corrosion mitigation performance of the synthesized molecules on mild steel (MS) in 0.5 M sulfamic acid (SA) was explored using gravimetric and electrochemical techniques. The obtained results demonstrated superior corrosion protection, with decrease in corrosion current density from 1.296 to 0.0778 mAcm⁻² at 303 K and from 1.783 to 0.2467 mAcm⁻² at 323 K with increase in IMTSC concentration. IMTSC was able to provide nearly 90% of inhibition efficiency (% IE) at all the studied temperature. The charge transfer resistance (R_ct) increased by many folds in the presence of IMTSC indicating the resistance towards metal dissolution in acid medium. Corrosion mitigation by IMTSC is mainly driven through physisorption, as supported by thermodynamic parameter analysis. Density Functional Theory (DFT) calculations, along with Molecular Electrostatic Potential (MEP) and topology analyses, offer deeper insights into the experimental findings related to inhibition efficiency of IMTSC. The surface morphology of the test specimen examined through scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy confirmed the adsorption of IMTSC molecules onto the specimen surface.